Racing:Mouse Morris stresses War Of Attrition has not met with a setback but has admitted the 2006 Cheltenham Gold Cup winner is unlikely to be seen this season.
The eight-year-old, who also finished runner-up to Brave Inca in the Supreme Novices' Hurdle in 2004, injured a tendon when being prepared for his defence of the blue riband event.
He underwent stem cell surgery, which was a success, and while he is now back in work, Morris thinks it would be asking too much to have him ready in time for Cheltenham.
"He's had absolutely no setback and the horse is in absolutely terrific fettle but he won't be running this year," said Morris.
"We are not rushing him back, he is in strong work but we decided that time was running out.
"It is not even nine months since he had the surgery. Normally it takes a year before they are even being ridden out but he has been ridden for the last six months.
"He's in great fettle and the owner (Michael O'Leary), myself and David Chapman-Jones, (vet) who did the stem cell work, are delighted with the scans but feel it would be pushing it to get him 100 percent.
"Had it have happened at the start of last season I would definitely say he would be running, but considering it is not even nine months, they have done a great job with him.
"It was always unlikely that he would run within the 12 months and you only have to look at Kicking King, who has been off two years with a similar problem.
"Everybody is happy with him but we just thought it would be rushing the job to try and get him ready."